What happened
On 13 June 2010, a Swearingen SA 226 TC Metro II, registration ZS-ZOC, was operating a domestic charter flight from Lanseria International Airport (FALA) to Polokwane Airport (FAPP). The aircraft was carrying two crew members and thirteen passengers when the flight crew noticed a red warning light indicating the undercarriage was unsafe during their approach to Polokwane.
Upon inspection by Air Traffic Control, it was observed that while the left main landing gear doors were partially open, the gear itself had failed to extend. The crew attempted several cycles of the landing gear and performed emergency extension procedures, including maneuvers to use G-forces to assist deployment, but the left main gear remained retracted.
Deciding to return to the better-equipped facilities at Lanseria, the crew performed a series of holding patterns. Before the final approach, the crew prepared for a forced landing by retracting the gear, shutting down both engines, feathering the propellers, and cutting all electrical power. The aircraft performed a controlled belly landing on Runway 2/24R, sliding on its lower fuselage before coming to a gradual stop. All 15 occupants escaped without injury, though the aircraft sustained substantial damage.
The investigation
The SACAA AIID investigation examined the mechanical failure and the maintenance history of the aircraft. Investigators looked into the possibility of the left main gear being obstructed by the gear doors or the tires. It was noted that the aircraft had recently undergone a maintenance check, but several anomalies were discovered.
Specifically, the investigation found that the maintenance organization had released the aircraft to service despite several unrectified electrical and avionic defects. Furthermore, the investigation identified that the aircraft was being operated commercially despite not yet being officially added to the operator's authorized aircraft list due to administrative delays within the regulatory authority.
Findings
- The primary cause of the accident was the pilot executing a wheels-up emergency landing following the failure of the left main landing gear to extend.
- A significant contributing factor was that the newly installed tires on the main landing gear did not comply with the width specifications outlined in the Fairchild Service Letter 226-SN-131.
- The shoulder width of the tires was found to be wider than permitted, which may have caused the gear to snag on a ledge on the inboard door skin during extension.
- The maintenance organization (AMO) provided a certificate of release to service despite known outstanding defects and lacked the necessary traceability for certain maintenance activities.
- The operator was using the aircraft for commercial purposes before the registration ZS-ZOC had been formally approved for their Air Operating Certificate.